Electrical coil with a tap changing means



I Aug. 27, 1968 A. w. BARBER 3,39

ELECTRICAL COIL WITH-A TAP CHANGING MEANS Filed March 30, 1967 2 Sheets-Sheet l FIG 2 INVENTOR.

AL FRED W BARBER WWW ATTORNEY g- 1958 A. w. BARBER 3,399,364

ELECTRICAL COIL WITH A TAP CHANGING MEANS Filed March 30, 1967 2 Sheets-Sheet 2 9 7 E6 /5 fi M4 o o o o o 7 o-p o ,o Q/

I als FIG 3 FIG 5 INVENTOR. ALFREDwBnRBa rBYW MM ATTORNEY United States Patent 3,399,364 ELECTRICAL COIL WITH A TAP CHANGINGMEANS Alfred W. Barber, Bayside, N.Y., assignor to Forbro Dei(gnkCorp., New York, N;Y., a corporation of New or Filed Mar. 30, 1967, Ser. No. 627,212 7 Claims. (Cl. 336-107) ABSTRACT OF THE DISCLOSURE Amulti-layered electrical coil has a comb of insulating material that supports and positions the top layer of the coil. A bridge member is supported on the top of the comb above the coil. There are a plurality of holes in the bridge member through which tap screws can be placed.

The present invention concerns methods of and means for providing readily changeable taps on the coil of an alternating current transformer or the like.

In their basic forms alternating current transformers consist of a primary to be connected to a source of alternating current and a secondary to be connected to a load or utilization means. The usual purpose of such transformers is to change the source or line voltage to a useful higher or lower secondary voltage. The secondary voltage will be determined by the source voltage and the ratio of the number of turns on the primary to the number of turns on the secondary. It is common practice to provide means for varying the secondary voltage by varying the turns ratio as by taps connected to a multi-point switch or by means of a sliding contact passing over a track for-med by a bare area on the top layer of the secondary winding. These are relatively expensive devices but may be required were it necessary to change the secondary voltage frequently.

The present invention concerns a simple and inexpensive way of providing a tap on the primary or secondary where frequent changing is not required but where an initial or infrequent change in secondary voltage is required. The method of the present invention is particularly intended for tapping a winding of heavy wire as in a transformer intended to supply a relatively heavy secondary current.

Briefly, the present invention consist of raising alternate turns of the top layer of a winding along one line and the remaining turns along an adjacent line. A bridge over the winding along these two lines is provided with hole opposite each of the raised areas. A contact screw in the appropriate hole in the bridge provides the tap contact at the desired voltage point. The raising of the wire to provide a point of contact permits making contact without shorting turns. The raising of alternate turns permits selecting the tap point one turn at a time. The tap points on the winding are maintained by a specially constructed comb lying under the turns and raising them at the required tap points.

Accordingly, one object of the present invention is to provide a method of and means for tapping a winding of an alternating current transformer.

Another object is to provide means for providing low resistance taps on a winding of an alternating current transformer for carrying heavy current.

Still another object is to provide means for tapping adjacent turns of an alternating current transformer without danger of shorting one turn to another.

A further object is to provide a low resistance and easily changed tap on a coil of an alternating current transformer.

These and other objects will be apparent to those skilled I 3,399,364 Patented Aug. 27, 1968 "ice FIGURE 2 is a view in. perspective of a. comb suitable for use in holding the turns of a coil to be tapped in accordance with the present invention.

FIGURE 3 is a side view of a detail oflthe present invention. H I

FIGURE 4 is a top view of anassembled transformer with tapping means in accordance with the present inv'eu: tion. J g '1 FIGURE 5 is a schematicfldiagrarn of one" possible transformer provided with tapping means infaccordance with the present invention. I I i FIGURE 1 shows a transformer with windingsl and including a top layer ofa number of turns two of which are designated 2 and 3. While this top layer is represented as-being wound of ribbon type wire, round wire can also be used. This top layer is Wound over a comb 4 (see FIG. 2) which is formed in such a manner as to raise alternate turns along two parallel lines and providing high points along these lines lying directly under a first row of tapped holes 6 and a second row of tapped holes 6' provided in a bridge piece 5. The bridge 5 is secured to the ends of comb 4 by suitable means such as screws 7 and 8. A tap contact is made on the desired turn of this top layer by means of a contact screw 9 threaded into one of the holes 6-6' lying just above the turn to be tapped, in this case turn 3.

FIGURE 2 shows one form of comb 4 suitable for use in the present invention. Holes 10 and 11 are for receiving the bridge mounting screws (7 and 8 in FIG. 1). The particular alternately angled turn supports 12, 13, 14, 15 and so on act to raise alternate turns to form two parallel rows of high points. Supports 12, 14, etc. provide one row and 13, 15, etc. the other. This comb 4 will generally be formed of insulating material such as a suitable plastic and, in quantity, may be molded or cast. The bridge 5 (FIG. 1) is either metal or insulating material. When made of metal, the connection to external circuitry may be permanently connected as by a lug, not shown, under either of screws 7 or 8. When made of insulating material, the connection may be made by a lug under the tap screw 9. It will be seen from FIGURES l and 2 that a tap screw which is fully as wide as a turn cross-section or wider to insure a low resistance contact capable of carrying the full coil current can be made by this method without danger of shorting turns. The comb, in addition, positions the turns accurately to align them with the holes for the tap screw.

FIGURE 3 is a side view showing the relationship between bridge 5 comb 4, coil turns 2, 3 and tap screw 9.

FIGURE 4 is a top view of an alternating current transformer incorporating the tapping device of the present invention. This transformer while in no Way intended to limit the invention to such, is wound on a shell core 15.

FIGURE 5 is a schematic circuit diagram of one form of transformer 20 provided with the tapping means of the present invention. This transformer 20 is illustrated as a flux oscillating transformer including a core 21, a magnetic shunt 22 and windings 23, 25 and 27. Winding 23 is shown as the primary intended to be connected to a source of alternating current 24. Winding 25 is the regulating winding and is resonated by a suitable capacitor 26. Winding 27 is the tapped output winding having output terminal 28 and 29. Output terminal 28 goes to one end of winding 27 while output terminal 29 goes to the tap point 30 which represents the tap 9 illustrated in FIGURES 1, 2, 3 and 4.

While only one form of the present invention has been of the invention as set forth, in particular, in the appended claims.

What is claimed is: I 1. An alternating current transformer including, th combination of, a multi-layer coil including a top layer winding, means for raising alternate turns of said top layer to uniform predetermined positions along at least two lines parallel to the axis of said coil, a contact screw for providing an electrical connection to one of said raised turns, and bridge means spanning said top layer, wherein said bridge means carries a plurality of holes positioned to lie in radial relationship to the raised areas of said top layer for holding said contact screw against a predetermined turn of said top layer.

2. A transformer coil tapping means as set forth in claim 1 wherein said bridge means is metallic.

3. A transformer coil tapping means as set forth in claim 1 wherein said holes are tapped.

4. A transformer coil tapping means as set forth in claim 1 wherein said raising means is a plastic comb device for supporting the top-layer turns as described in claim 1. I

5. A transformer 'coil tapping means as set forth in claim 1 wherein said multi-layer coil is the secondary of an alternating current transformer.

- 6.'A transformer coil tapping means as set forth. in claim 1 wherein said multi-layercoil is the primary of an alternatingcurrent transformer. p

7. A transformer coil tapping means as set forth in claim 1 wherein said coil is one of the coilsof a flux oscillating'transformer.

References Cited UNITED STATES PATENTS 2,466,961 8/1946 1 Nichol 336-l92 I FOREIGN PATENTS 731,018 12/1942 Germany.

LEWIS H. MYERS, Primary Examiner. E. GOLDBERG, Assistant Examiner. 

